During encystment, Giardia undergoes fundamental biological changes. We identified two unique cyst wall proteins, cwp1 and cwp2, as well as the ER resident chaperonin, Bip, which allowed us to study how the level and amount of these proteins are controlled, the nature of the vesicular transport of cwp 1 & 2 into encystment-specific vesicles, and the formation of the cyst wall. Cwp2 was identified, characterized and sequenced. Studies showed that it is secreted similar to cwp1 and likely forms a stable complex with cwp1. Bip expression increases markedly during encystment; however, in contrast to cwp1 and 2, control appears posttranscriptionally. The first description of protein isoprenylation in any protozoan was described in Giardia. This indicates posttranslational modification by farnesyl, and geranylgeranyl isoprenoids occurs in Giardia and is important in the regulation of growth of this primitive eukaryote. A panel of monoclonal antibodies were produced which recognize three of the four major species of microsporidia which infect humans.